A Multi-Proxy Approach to Understanding Late Pleistocene Climate Change in Namibia, Botswana, and Northwestern South Africa

虽然世界各地的科学家正在开发区域古植被和古气候重建，以更好地解决气候变化在过去影响这些地区的方式，但在非洲西南部进行的古环境研究相对较少。 该研究项目将是一个雄心勃勃的国际，多学科，非洲西南部古环境研究合作计划的第二阶段，包括纳米比亚和博茨瓦纳和南非的部分地区。 在这个项目的第一阶段，研究人员取得了一些重大发现。 第二阶段将继续获取南部非洲的古植被和古气候数据，这是改进当前生物群落和大气环流模型模拟所需的，以便更好地预测过去和未来的状况，包括全球持续变暖可能产生的影响。 研究人员采用了一种多代理的方法，在广泛的地区进行古气候研究，以评估气候在空间背景下的时间变化。 他们将检查的站点将提供今天在冬季获得相当大比例降雨的地区（如纳米比亚西南部和南非西北部）的数据，以及扎伊尔空气从大西洋带来的夏季降雨占主导地位的地区（主要是纳米比亚北方和博茨瓦纳北方）或印度洋（博茨瓦纳，南非西北部大部分地区和纳米比亚东部）。 研究人员的最终目标是结合联合收割机从凸起的海洋阶地和河流沉积物，潘/弦月和残留的线性沙丘系统，以及从春天的土丘，蹄兔middens，瀑布凝灰岩，洞穴洞穴的洞穴沉积物的数据，开发最详细和全面的晚更新世气候变化记录西南非洲，包括全新世的高分辨率记录。 他们特别感兴趣的是确定在北方半球和冰和海洋核心，包括末次冰期最大，新仙女木，全新世最佳，中世纪最佳，和小冰期确定的主要气候事件期间，在非洲西南部的条件。 AMS放射性碳、ICPMS U系列和光激发光测年将用于为各种数据集编制年表，预计该项目将作出若干重大的研究贡献。 调查人员希望能证明，在更新世晚期，纳米布沙海的北方边界在其目前的边界奎塞布河以南，如果不是干旱的话，也会质疑沙丘的古老性。 他们将为非洲任何地方提供最详细的全新世气候变化记录，以帮助那些使用大气环流模型的人。 它们将产生一个很长的记录（可能在现在之前的10万到35万年之间），可以与海洋核心，冰芯和太阳变化数据进行比较，从而可以更现实地解释南部非洲过去的气候变化。 研究人员不会只关注一个可能提供误导性，不完整或模糊结果的数据来源，而是将古代河流，湖泊和沙丘系统过去活动增加的证据与洞穴石笋获得的气候变化的高分辨率数据结合起来。 在这些半干旱和干旱环境中缺乏理想的花粉研究沉积物的情况下，他们将从过时的蹄兔中获得花粉，从而提供至少过去5万年的古植被数据。 因为这个项目是由来自纳米比亚、南非、西班牙和美国的十个不同机构的十名科学家进行的，它将促进国际合作。 纳米比亚和美国学生将获得资助，以便他们能够参与研究计划，一名来自西班牙的博士后研究员也将参与其中。我们的研究结果将通过在国际期刊上发表，以及在南非，纳米比亚和博茨瓦纳的期刊上发表。 该奖项由NSF国际科学与工程办公室共同资助。

Although scientists around the world are developing regional paleovegetation and paleoclimatic reconstructions in order to better address the ways that climate change has affected those regions in the past, relatively little paleoenvironmental research has been conducted in southwestern Africa. This research project will be the second phase of an ambitious international, multidisciplinary, collaborative program of paleoenvironmental research in southwestern Africa, including Namibia and parts of Botswana and South Africa. In the first phase of this program, the investigators made a number of significant discoveries. The second phase will continue the process of acquiring the paleovegetation and paleoclimatic data for southern Africa that is needed to improve current biome and general circulation model simulations so that they can better predict past and future conditions, including the possible impacts of continued global warming. The investigators have adopted a multi-proxy approach to paleoclimate research over a broad area in order to assess temporal variations in climate in a spatial context. The sites that they will examine will provide data for areas that today receive a significant proportion of their rain in winter (such as southwestern Namibia and northwestern South Africa), as well as areas that are dominated by summer rainfall brought from the Atlantic Ocean by Zaire air (largely northern Namibia and northern Botswana) or from the Indian Ocean (Botswana, most of northwestern South Africa, and eastern Namibia). The investigators' ultimate objective is to combine paleoenvironmental data from raised marine terrace and fluvial sediments, pan/lunette and relict linear dune systems, and data from spring mounds, hyrax middens, waterfall tufas, and cave speleothems to develop the most detailed and comprehensive late Pleistocene record of climate change for southwestern Africa, including a high-resolution record for the Holocene. They are particularly interested in determining conditions in southwestern Africa during major climatic events identified in the Northern Hemisphere and in ice and marine cores, including the Last Glacial Maximum, Younger Dryas, Holocene Optimum, Medieval Optimum, and Little Ice Age. AMS radiocarbon, ICPMS U-series, and optically stimulated luminescence (OSL) dating will be used to develop chronologies for the various data sets.This project is expected to make a number of significant research contributions. The investigators expect to show that the northern limit of the Namib Sand Sea was south of its present boundary, the Kuiseb River, during the late Pleistocene questioning the antiquity of the dunes if not the aridity. They will produce the most detailed record of Holocene climate changes for anywhere in Africa to assist those working with general circulation models. They will generate a long record (possibly to between 100,000 and 350,000 years before the present) that will enable comparison with ocean core, ice core, and solar variability data, thereby allowing more realistic explanations of past climate changes in southern Africa. The investigators will not focus on just one source of data that could provide misleading, incomplete, or ambiguous results but instead will bring together evidence of past increased activity in ancient fluvial, lake, and dune systems with higher-resolution data on climate change obtained from cave stalagmites. In the absence of ideal sediments for pollen studies in these semiarid and arid environments , they will obtain pollen from dated hyrax middens, thereby providing paleovegetation data for at least the last 50,000 years. Because the project is being undertaken by ten scientists from ten different institutions in Namibia, South Africa, Spain, and the U.S., it will foster international collaboration. Namibian and American students will be provided funding so that they can participate in the research program, and one post-doctoral researcher from Spain will also be involved. The results of our research will be made available through publication in international journals, as well as in South African, Namibian, and Botswana journals. This award is jointly funded by the NSF Office of International Science and Engineering.